The purposes of these studies are to explore factors affecting fetal oxygenation and growth in-utero. We have formulated an hypothesis for the control of cardiac output and are carrying out experiments to test it in sheep and rabbits. We are studying the transfer of water and carbon dioxide across the placenta. We are developing mathematical models of the effects of uterine contractions on fetal oxygenation. We are comparing the effects of steady state vs. intermittent hypoxia on fetal survival in rabbits. BIBLIOGRAPHIC REFERENCES: Power, G.G. and L.D. Longo. Placental O2 Transfer and Fetal Consumption at Varying Fetal Arterial PO2. Fed. Proc. 34(3):451, 1975; Allen, W.W., G.G. Power and L.D. Longo. A Mathematical Model of the Time Course of PO2 Changes in the Circulation. Fed. Pro. 34(3):353, 1975.